1. Field
This disclosure teaches techniques related to a handwriting trajectory recognition system, and more particularly, to techniques for recognizing handwriting trajectory in three-dimensional space.
2. Description of the Related Art
Recently the markets for personal mobile devices such as PDAs, cellular phones, notebooks, and so on, have increased. It can be stated that such personal mobile devices are most fit for ubiquitous environments since they are easy to carry and used for information utilization anytime and anywhere. That is, the recent mobile devices enable users to utilize information during their movements so that the users can use information any time and anywhere, unlike the past environments confining information utilization to immobile devices such as desktop personal computers (PCs) installed at homes.
However, while such mobile devices have been made smaller for convenience in carrying, they have become inconvenient in recognizing information and inputting commands through the display part of the devices. In such mobile devices, making it easy to carry runs counter to being easy to input and output information. Therefore, researches and developments have been continuously made on methods for overcoming the problems.
Recently, a pen-type input system has emerged as a means through which users use the mobile devices more conveniently. A general pen-type input system is designed to recognize writing trajectory or selection motions which are input through a two-dimensional plane of an input pad so that the a mobile device displays writing trajectories on a display unit or performs corresponding operations based on recognized information.
FIG. 1 is a view for showing an input style for a conventional pen-type input system. The pen-type input system has a stylus pen part 10 held in a user's hand so that a user can make writing or selecting motions with it. It further includes a display part 22, which may be a PDA 20, for example, that recognizes menu selection commands and/or writing trajectories from a contact state of a portion of the stylus pen part 10 on the two-dimensional plane of the display part 22. The display part displays corresponding operations based on a selected menu or handwritings. Herein, the pen part 10 operates as a pointing tool or handwriting tool without an extra power supply, and the PDA 20 processes a signal corresponding to a portion of the display part 22 on which the tip portion of the pen part 10 is placed.
The pen-type input system as above decides what information is input depending upon positions where the pen part 10 is in contact with the two-dimensional plane of the display part 22. That is, if a current view displayed on the display part 22 is a view displaying menus, the PDA 20 decides information corresponding to a position where the tip portion of the pen part 10 is in contact with as menu selection information. It then executes a corresponding command based on information on the selected position. Further, the PDA 20 obtains information on contact positions of the pen part 10 that are continuously changing, if a view capable of recognizing handwritings is displayed. It then displays on the view of the display part 22 the handwriting trajectory from the obtained information.
The above pen-type input system can more precisely recognize handwritings since a user writes on the display part of two-dimension plane. However, the user must perform his or her menu selections or writing motions within a limited view of the display part 22, which still causes inconvenience in inputting users' input motions.
In order to solve the above problem, systems having motion-detecting sensors inside the pen part 10 and detecting through the sensors users' handwriting trajectories in the three-dimensional space have been proposed in U.S. Pat. No. 6,181,329 (laid-open Jan. 30, 2001) and U.S. Pat. No. 6,212,296 (laid-open Apr. 3, 2001).
The Pen-type input systems disclosed in the U.S. Pat. Nos. 6,181,329 and 6,212,296 can recognize writing motions carried out in the three-dimensional space so that a user can input information without any limit to a writing area. However, these systems have a problem that there exists a high possibility of causing recognition errors since consonants and vowels or diverse symbols such as alphabets and the like are continuously generated when users make writing motions in the three-dimensional space. When most people make writing motions, they write consonants and vowels or symbols such as alphabets and the like in stroked lines separately from each other in order for third parties to more easily grasp the handwritings. While, the above pen-type input system using the writing plane interprets high-frequency signals based on frictions between the pen and the writing plane to recognize stroked lines for consonants, vowels, symbols such as alphabets and the like, the pen-type input system recognizing writing motions in three-dimensional space cannot recognize stroke lines any more since those lines are continuous in the three-dimensional space. Accordingly, when needed to display on a display unit writing trajectories based on writing motions in the three-dimensional space, the system can display only continuous handwriting trajectories that are different from users' intents. This causes a problem since a third party has difficulties in recognizing information.
However, techniques are unavailable for segmenting strokes into only symbols for pure writings with respect to symbols based on writing motions in space without an extra writing plane and recognizing only the symbols for pure writings.